Leech

A leech is a segmented, soft-bodied worm that belongs to the subclass Hirudinea, commonly found in freshwater, marine, and terrestrial environments. Many leeches are hematophagous, meaning they feed on blood, attaching to hosts using specialized mouthparts and secreting an anticoagulant to facilitate blood flow. While some leech species are used medically for bloodletting and increasing circulation, most are natural decomposers or predators, helping control populations of other invertebrates. Their unique ability to attach securely and extract blood symbiotically makes them notable in both ecological systems and medical applications.